1. Field of the Invention
This invention relates to electroless metal plating of aramid fibers wherein the metal is strongly adhered to the aramid fiber substrate and provides a highly conductive surface. The aramid is subjected to a preplating treatment including carefully controlled exposure to a concentrated aqueous nitric acid solution or a dilute concentration of chlorosulfonic or fluorosulfonic acid in an organic liquid, followed by washing, catalyzation, and the electroless plating, itself.
2. Description of the Prior Art
Electroless plating is the deposition of a metal film by interaction of metal ions and a chemical reducing agent in a basic solution. Electroless plating, in a general way, is well known. One of the difficulties in achieving successful electroless plating has resided in obtaining good adhesion between the plating substrate and the plated metal. While mere encapsulation may suffice for some applications and some articles, good adhesion of the plated metal is essential for fiber surfaces because the plated metal coating must be durable enough to withstand the forces of further processing and end use stresses.
U.S. Pat. No. 5,302,415, issued Apr. 12, 1994 discloses a process for making electroless plated aramid surfaces by means of a preplating treatment using 80 to 90 weight percent aqueous sulfuric acid.